In communications networks, there may be a challenge to obtain good performance and capacity for a given communications protocol, its parameters and the physical environment in which the communications network is deployed.
For example, increase in traffic within communications networks such as mobile broadband systems and an equally continuous increase in terms of the data rates requested by end-users (wireless devices) accessing services provided by the communications networks may impact how cellular communications networks are deployed. One way of addressing this increase is to deploy lower-power network nodes, such as micro or pico radio base station (RBS) network nodes (hereinafter denoted PBS), within the coverage area of a macro cell served by a macro base station (MBS) network node. Examples where such additional network nodes may be deployed are scenarios where end-users are highly clustered. Examples where end-users may be highly clustered include, but are not limited to, around a square, in a building, such as an office or a shopping mall, or along a road in a rural area. Such a deployment of additional network nodes is referred to as a heterogeneous or multi-layered network deployment, where the underlying layer of low-power micro or PBS network nodes does not need to provide full-area coverage. Rather, low-power network nodes may be deployed to increase capacity and achievable data rates where needed. Outside of the micro- or PBS-layer coverage, end-users would access the communications network by means of the overlaid macro cell.
Backhauling based on the Long Term Evolution (LTE) telecommunications standards may be carried either over normal IMT-bands, e.g. the 2.6 GHz frequency band, or by running LTE baseband communications on higher radio frequencies, such as in the 28 GHz frequency band. LTE based backhauling implies that the PBS network nodes are connected to a client node which is used to create a wireless link to a hub node.
In any of the above two cases, the wireless links are typically managed by LTE core control mechanisms. For example, the LTE Mobility Management Entity (MME) may be utilized for session control of the LTE links, and the Home Subscription Service (HSS) may be utilized for storing security and Quality of Service (QoS) characteristics of the wireless links of individual wireless end-user terminals embedded in the PBS network node.
Moreover, in practice more than one client node may connect to a common hub node. This implies support for Radio Resource Management (RRM) functions, such as scheduling and prioritization of the traffic to and from the different clients, at the hub node.
To each client node there might be several PBS network nodes, each of which may offer one or several different radio access technologies, such as based on the Universal Mobile Telecommunications System (UMTS), LTE, or IEEE 802.11x to the wireless end-user terminals of the end-users. Therefore there is a need to differentiate between the corresponding backhaul traffic to different nodes in the communications network. For example, any LTE compliant traffic may need to end up in nodes such as the serving gateway (S-GW) or the MME and any WiFi compliant traffic may end up in an edge router or an Evolved Packet Data Gateway (ePDG).
Moreover, for a given radio access technology (RAT), QoS differentiation is provided to the end-users (i.e., to the wireless end-user terminals of the end-users) so that e.g. guaranteed bitrate (GBR) services, such as voice calls, will not be disturbed by best effort (BE) services, such as web browsing. In order to enable this, QoS differentiation is needed also on the backhaul links.
If the wireless backhaul is based on LTE, there are tools that provide both the routing functions and QoS differentiation, such as based on the LTE bearer concept. Typically then, for each type of RAT, one GBR and one BE bearer are established on the backhaul links.
In general terms, using wireless backhaul links for micro/pico base stations provides simpler deployment and connection compared to wired backhaul links. For high traffic, this puts a demand on the performance of the wireless backhaul link as it may become a bottleneck. In situations where, for example, the path gain of a wireless device to another base station is better than to the base station currently serving the wireless device, the serving base station may determine to perform a handover of the wireless device to the other, target, base station. This involves performing steps, as outlined in the document 3GPP TS36.300, FIG. 10.1.2.1.1-1 for the case of X2-based handover.
However, there is still a need for an improved forwarding data to a wireless terminal.